1. Primary charge rollers are used in laser printer toner cartridges to help control the quality of printing. The primary charge roller is a steel shaft covered with a plastic coating to a diameter of approx. 0.50". The quality of the primary charge roller in the toner cartridge is extremely important to ensure a properly functioning toner cartridge producing a consistent product in long runs of printing.
2. The quality of primary charge rollers can in part be determined by leakage current (conductivity) between the steel shaft of the roller and the roller covering.
3. It is possible to accurately measure leakage current under controlled conditions.
4. Prior state of the art tests involve:
a. A short test run in a printer which does not prove that the primary charge roller will function properly in long runs of printing. PA1 b. Voltage is applied, through a microammeter, to the steel shaft and the covering of the primary charge roller by means of a probe. The value is then indicated on the microammeter, (FIG. 1). PA1 a. The primary charge roller evaluator measures leakage current over the entire surface of the roller. This is accomplished by totally encasing the primary charge roller in a conductive material, the upper and lower holders. The prior state of the art, by a hand held probe, only measures leakage current at a single point or a limited number of points along the primary charge roller, not the entire surface, therefore, a substandard roller may appear acceptable based on the point(s) measured. PA1 b. The primary charge roller evaluator provides positive premeasured consistent pressure along the entire roller via a self-locking latch to ensure proper contact and provide consistent true and accurate readings. The prior state of art, by hand held probe, had no consistent pressure and thus provided inconsistent and inaccurate measurements. PA1 c. The primary charge roller evaluator compensates for variances in humidity. The prior state of art method does not account for changes in humidity which does affect accurate readings.
(1.) This test does not prove the quality of the primary charge rollers because readings vary at different location of the probe on the roller. PA2 (2.) Readings vary due to differences in pressure on the probe. PA2 (3.) Readings on microammeter vary due to changes in leakage current caused by reaction of primary charge roller to humidity changes.